Catalytic Activity For Hydrogen Production Research Articles

Enhanced catalytic activity in hydrogen production from hydrolysis of sodium borohydride using starch hydrogel-CoNi bimetallic alloys

In this article, starch hydrogel was successfully prepared using a citric acid cross-linking method and was used as a template to synthesize starch hydrogel-CoNi bimetallic alloys by the in situ reduction in Co2+ Ni2+ ions using NaBH4 as the reducing agent in the presence of the starch hydrogel network. The starch hydrogel-CoNi bimetallic alloys were simply isolated by filtration and also characterized by SEM, TEM, TGA, FTIR and XRD, respectively. The catalytic activity of starch hydrogel-CoNi bimetallic alloys was used as a catalyst in the hydrogen production from the hydrolysis of NaBH4 in the presence of alkaline solution. The variables affecting on the hydrolysis of NaBH4 such as the initial CoNi molar ratio, initial NaOH concentration, catalyst amount, initial NaBH4 concentration and reaction temperature were examined. The activation energy (Ea), the activation enthalpy (∆H#) and the activation entropy (∆S#) were found to be 36.24 kJ mol−1, 37.75 kJ mol−1 and − 125.23 kJ mol−1 K−1, respectively. The catalyst can be used up to 5 times with 100% conversion, and the catalyst was remained 68% activity after storing 15 days. This approach offers a great potential to utilize starch hydrogel acting as a biocompatible material for a large-scale synthesis of bimetallic alloys for various applications in catalysis.

Simple synthesis of Cu2O–CoO nanoplates with enhanced catalytic activity for hydrogen production from ammonia borane hydrolysis

The development of inexpensive and high performing catalysts for ammonia borane (NH3BH3) hydrolysis is crucial for hydrogen production. In our research, a high-performance plate-like Cu2O–CoO nanocomposite catalyst for NH3BH3 hydrolysis has been developed for the first time. In the hydrolytic reaction, both Cu2O and CoO are separately inactive, while Cu2O–CoO nanoplates show a high turnover frequency of 34.1 molhydrogen min−1 molcat−1, which is attributed to the synergistic effect between Cu2O and CoO. It is interesting to discover that the induction time for the hydrolytic reaction is reduced to null when a small amount of Cu2O is introduced into CoO. The reaction kinetics of NH3BH3 hydrolysis catalyzed by Cu2O–CoO is also investigated. This work may provide other researchers some valuable insights into designing inexpensive and synergistic catalysts with enhanced catalytic activity for NH3BH3 hydrolysis for hydrogen production.

Galvanostatically Deposited Ptni Thin-Films As Electrocatalytists for the Hydrogen Evolution Reaction

Hydrogen renders high energy density without any direct carbon emissions, which makes it an ideal energy carrier [1]. PtNi nanomaterials exhibit high catalytic activity for hydrogen production through the hydrogen evolution reaction (HER), in some cases superior to bare Pt [2] and with lower cost due to the replacement with Ni. Efforts devoted to the synthesis of PtNi nanomaterials, most of them based on solvothermal methods [3,4], involve several steps and reaction times amounting to hours. Electrochemical deposition is a fast and simple method that allows high control over the morphology of the deposits. Previously, our group used single-pulse galvanostatic electrodeposition to generate Ni thin-layers on gold electrodes; the Ni deposits exhibited high catalytic activity for methanol electro-oxidation [5]. In this work we investigate the catalytic activity of galvanostatically generated PtNi deposits on gold towards HER in alkaline media.After mechanical polishing and electrochemical cleaning of a Au electrode, the electrodeposition was carried using a 1.5 mM K2[PtCl4] + 50 mM NiSO4 + 500 mM NaCl plating solution saturated with N2. Figure 1a shows the typical E – t transient response to a two seconds current pulse. Its stair-like shape hints the presence of at least four electrochemical reactions, identified as regions I to IV. Based on the Nernst potentials (horizontal dashed lines) and the processes reported for nickel by Salinas et al. [5], regions I and II can be assigned to Pt deposition, Ni deposition and hydrogen evolution from H+ reduction to region III, and hydrogen evolution form water reduction to region IV. The effect of the applied current density on the potential transients is shown in Fig. 1b, higher values lead to shorter durations of each stage and lower potential values. The presence of Ni and Pt was confirmed by cyclic voltammetry in 1 M KOH and 50 mM H2SO4, respectively, but no particles could be detected by SEM, which suggest that thin films were formed. Liu et al. [6] and Wang et al. [7] reported the electrodeposition of Pt and Ni thin films which were self-terminated by potential pulses negative enough to favor the formation and adsorption of species blocking further growth of the deposits. Since during the galvanostatic deposition the electrode reaches potential values negative to the self-termination threshold, it its likely that a thin layered PtNi films were formed.The activity of the PtNi deposits towards HER was evaluated by linear sweep voltammetry in 1 M KOH. The overpotentials required to attain a current of 10 mA cm-2 (η 10) were 64 mV for the deposit obtained at 8 mA cm-2, while the highest overpotential, 77 mV, was obtained at 2 mA cm-2. The η 10 of the PtNi/Au deposits falls within the range reported for similar materials: 39 mV[4] to 186 mV [8]. However, the specific current at 38 mV of the most active material obtained, 6390 A gPt -1, is far larger that the one of the most active material reported in the literature of 1740 A gPt -1 [4]. This may be attributed to an optimal Pt/Ni ratio and a thin-layered deposit, achieved by the complex potential trajectories generated by galvanostatic electrodeposition. Tafel plots (Fig. 1c) exhibited two linear regions, with values independent of applied current density of deposition: 35 mV dec−1 for the first slope and 100 mV dec−1 for the second one. This suggests that HER follows the same pathway on all the deposits and the Heyrovsky reaction is the limiting step [8].Figure1 a) Typical potential transient recorded during the galvanostatic deposition of PtNi. b) Potential transients recorded during a galvanostatic deposition of PtNi on a clean Au electrode at different j dep. c) Tafel plots for the deposits produced at different current densities.

Ligand-based electronic effects on the electrocatalytic hydrogen production by thiosemicarbazone nickel complexes.

This work reports on the synthesis and characterization of a series of mononuclear thiosemicarbazone nickel complexes that display significant catalytic activity for hydrogen production in DMF using trifluoroacetic acid as the proton source. The ligand framework was chemically modified by varying the electron-donating abilities of the para substituents on the phenyl rings, which was expected to impact the capability of the resulting complexes to reduce protons into hydrogen. Over the four nickel complexes that were obtained, the one with the thiomethyl substituent, NiSCH3, was found to overtake the catalytic performances of the parent complex NiOCH3 featuring lower overpotential values and similar maximum turnover frequencies. These results confirm the electronic effects of the ligand on HER when using thiosemicarbazone nickel complexes and support that chemical modifications can tune the catalytic performances of such systems.

Biomass-Derived Nickel Phosphide Nanoparticles as a Robust Catalyst for Hydrogen Production by Catalytic Decomposition of C2H2 or Dry Reforming of CH4

Nickel is well recognized for its high catalytic activity in hydrogen production and hydrotreating, but it experiences severe deactivation upon coke formation. The development of a nickel-based catalyst that is resilient to deactivation while maintaining its signature high activity is therefore desirable. We demonstrate a simple but effective technique for the synthesis of nickel phosphide catalysts by impregnating nickel into carbonized natural cellulose fibers (NCFs) that naturally contain phosphorus. At a sufficient annealing temperature (1100 °C), the nickel particles react with phosphorus, forming Ni2P and Ni5P4 nanoparticles. Higher annealing temperatures (>1500 °C) promote the formation of single atom nickel, which greatly supplements the catalytic performance. Our nickel phosphide catalyst exhibits a markedly superior activity and stability in the synthesis of hydrogen by C2H2 decomposition and the dry reforming of methane (DRM) compared to the Ni/Al2O3 model catalyst. The sustained activity and s...

Organosiloxane tunability in mesoporous organosilica and punctuated Pd nanoparticles growth; theory and experiment

Abstract The synthesis of mesoporous organosilicas (MOs) using co-condensation for a high ratio of a long and flexible chained organosiloxane bridge with silica precursor (e.g. tetraethylorthosilicate (TEOS)) is a complex and challenging task. By complementing the experimental characterisations with density functional calculations, The critical ratio of the urea-based organosiloxane bridge (BTPU) to tetraethyl orthosilicate of 1:8 was identified to delivers reliably stable urea bridged MO (MO-urea) with relatively large surface area and mesoporosity. Moreover, the Pd nanoparticles supported on the pore channels of MO-urea achieve a narrow distribution size averaging at a diameter of ~2 nm. This fine distribution is driven by the Pd nanoparticles nucleating only on the exposed SiO2 section of MO-urea while the BTPU bridges punctuate the growth of the Pd nanoparticles limiting their size. As a result, the obtained Pd@MO-urea exhibits excellent multifunctional catalytic activity for hydrogen production from formic acid and p-nitrophenol (PN) reduction in aqueous media with four folds increase in yield compared to the non-punctuated Pd nanoparticles.

Hydrogen Production from Formic Acid over Au Catalysts Supported on Carbon: Comparison with Au Catalysts Supported on SiO2 and Al2O3

Characteristics and catalytic activity in hydrogen production from formic acid of Au catalysts supported on porous N-free (Au/C) and N-doped carbon (Au/N-C) have been compared with those of Au/SiO2 and Au/Al2O3 catalysts. Among the catalysts examined, the Au/N-C catalyst showed the highest Au mass-based catalytic activity. The following trend was found at 448 K: Au/N-C > Au/SiO2 > Au/Al2O3, Au/C. The trend for the selectivity in hydrogen production was different: Au/C (99.5%) > Au/Al2O3 (98.0%) > Au/N-C (96.3%) > Au/SiO2 (83.0%). According to XPS data the Au was present in metallic state in all catalysts after the reaction. TEM analysis revealed that the use of the N-C support allowed obtaining highly dispersed Au nanoparticles with a mean size of about 2 nm, which was close to those for the Au catalysts on the oxide supports. However, it was by a factor of 5 smaller than that for the Au/C catalyst. The difference in dispersion could explain the difference in the catalytic activity for the carbon-based catalysts. Additionally, the high activity of the Au/N-C catalyst could be related to the presence of pyridinic type nitrogen on the N-doped carbon surface, which activates the formic acid molecule forming pyridinium formate species further interacting with Au. This was confirmed by density functional theory (DFT) calculations. The results of this study may assist the development of novel Au catalysts for different catalytic reactions.

Cr–doped ZnS semiconductor catalyst with high catalytic activity for hydrogen production from hydrogen sulfide in non-thermal plasma

Abstract A series of Al2O3 supported Cr-doped ZnS semiconductor catalysts with various Cr/Zn molar ratios were prepared by co-impregnation method, and investigated in non-thermal plasma induced H2S decomposition. The as-synthesized catalysts were characterized using XRD, N2 adsorption/desorption, UV-visible spectroscopy, TEM, Raman, ICP and XPS techniques. Cr-doped ZnS with different amount of Cr possessed the significantly enhanced catalytic performance, compared to undoped ZnS. Variations in catalytic activity are discussed in terms of modification on the chemical and physical properties of the Cr–doped ZnS catalysts. Among all the catalysts, the Cr0.20-ZnS catalyst showed the best catalytic behavior with full H2S conversion at lowest energy cost. Furthermore, the long-term study demonstrates that Cr–doped ZnS exhibits good stability in H2S decomposition.

Effective hydrogen production from partial oxidation of propane over composite Ni/Al2O3[sbnd]SiC catalyst

In this work, hydrogen production from partial oxidation (POX) of propane over composite Ni/Al2O3SiC catalyst was investigated. In order to utilize the high thermal conductivity and chemical stability of SiC, the composite Al2O3SiC support of the catalyst was synthesized by precipitation technique, then Ni component was loaded using impregnation method. The as-prepared samples were characterized by X-ray diffraction, BET, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. As observed, stacking porous structures were appeared after calcination process by doping SiC with certain ratios. According to the stiochiometric ratio, a C3H8O2 (1:1.5) gas mixture was used to study the catalytic activity for hydrogen production from POX of propane. From the results, local overheat of the catalyst bed generated by the exothermic reactions was relieved by doping SiC and Ni/Al2O3SiC (30 wt%) catalyst performed a higher hydrogen production. Aggregation and carbon deposition of Ni/Al2O3SiC (30 wt%) catalyst were reduced compared to Ni/Al2O3 from the observation of SEM and TEM with H2 production up to around 236 μmol/gcat·s and kept stable for 26 h at 600 °C. By means of TGA, non-isothermal oxidative decarburizations of the spent catalysts were studied. It was found that less carbon deposit and lower activation energy for oxidative decarburization were found by doping SiC to Ni/Al2O3.

Preparation of carbon supported Pt-Ni alloy nanoparticle catalyst with high metal loading using cation exchange resin and its application for hydrogen production

Formic acid has been attracting interest as a promising hydrogen carrier because hydrogen can be produced over the catalysts under mild condition with low energy input. Though the catalytic activity for hydrogen production from formic acid is enhanced by increasing the metal loading, the trade-off between high metal loading and small metal particle size practically occurred with carbon catalyst prepared by impregnation method. To overcome this challenge, we herein utilized a noble catalyst preparation method which uses an ion-exchange resin as an initial carbon material. Five compositions of carbon supported Pt-Ni alloy catalysts were successfully prepared at high metal loading (25–50 wt%) with small metal particle sizes (2.3–3.8 nm observed by TEM). The metal particles were embedded in the carbon, which was contributed to small particle size of the loaded metal. The hydrogen production from formic acid was investigated over the prepared catalysts at 100–200 °C. It was elucidated that the turnover frequencies of Pt50Ni50/C and Pt75Ni25/C were higher than that of Pt/C at above 175 °C, suggesting that the decrease of Pt content without losing their catalytic activity could be achieved by Pt50Ni50/C and Pt75Ni25/C due to alloy formation. To further enhance the catalytic activity by increasing the active metal surface area, supercritical water treatment at 400 °C for 1 h was utilized. The metal surface area of catalysts was noticeably increased due to the gasification of the carbon support nearby metal particles. Formic acid conversion, likewise, drastically increased after the treatment.

Synthesis of Ni/CaO-γ-Al2O3@Ru Core Shell via Micro-Emulsion Method for Bio-oil Steam Reforming of Empty Fruit Bunch

Hydrogen production from bio-oil steam reforming plays an important role in the development of renewable hydrogen from biomass to produce the cleanest fuel. However, the existence of coke and low carbon conversion are problems that have been found in some studies. The purpose of this study was to reduce coke formation and to enhance carbon conversion by using core shell nanoparticle catalysts that could increase of surface area, support interaction and its catalytic activity for hydrogen production from bio-oil steam reforming of empty fruit bunch (EFB). Ni/CaO-γ-Al2O3@Ru core shells were prepared by CTAB/n-hexanol/n-hexane/water micro-emulsion system. The catalysts were characterized by means XRD, BET, FESEM-EDS and TEM. Bio-oil aqueous fraction was analyzed by using GC-MS. Carbon conversion and hydrogen yield by using Ni/CaO-γ-Al2O3@Ru core shell are resulted more 68.4 % and 18.6% than using Ni/CaO-γ-Al2O3 catalyst, respectively. The highest hydrogen yield by using Ni/CaO-γ-Al2O3@Ru core shell for steam reforming bio-oil is 5.6% in minute 10 with 0.07 g of coke deposit. The study concludes that the effect of Ni/CaO-γ-Al2O3@Ru core shell is more efficient in hydrogen production, carbon conversion and coke deposit compared to Ni/CaO-γ-Al2O3 catalyst

Comparison between in-situ and ex-situ catalytic pyrolysis of sawdust for gas production

In this work, in-situ and ex-situ catalytic pyrolysis (CP) of sawdust by Ni-based and Cu-based catalysts are compared in a two-stage fixed bed reactor. Alkali metal K and alkaline earth metal Mg are used to modify the catalysts for comparison. The ex-situ configuration plays a more dominant role in reducing tar while increasing gas production for all catalysts. Reduced Ni shows the best catalytic activity for hydrogen production, obtaining 36.4 vol.% of hydrogen with a yield of 13.6 mmol/g-bio in ex-situ CP. With the increase of temperature, ex-situ CP has a more significant effect on improving gas product and reducing liquid product than in-situ CP. K presents better modification effect than Mg, resulting in a higher yield of gaseous products. Also, TG and Raman analysis indicate that K can decrease the amount of coke deposition on catalysts and make the coke easier to be removed.

FeFe]‐Hydrogenase Mimetic Metallopolymers with Enhanced Catalytic Activity for Hydrogen Production in Water

AbstractElectrocatalytic [FeFe]‐hydrogenase mimics for the hydrogen evolution reaction (HER) generally suffer from low activity, high overpotential, aggregation, oxygen sensitivity, and low solubility in water. By using atom‐transfer radical polymerization (ATRP), a new class of [FeFe]‐metallopolymers with precise molar mass, defined composition, and low polydispersity, has been prepared. The synthetic methodology introduced here allows facile variation of polymer composition to optimize the [FeFe] solubility, activity, and long‐term chemical and aerobic stability. Water soluble functional metallopolymers facilitate electrocatalytic hydrogen production in neutral water with loadings as low as 2 ppm and operate at rates an order of magnitude faster than hydrogenases (2.5×105 s−1), and with low overpotential requirement. Furthermore, unlike the hydrogenases, these systems are insensitive to oxygen during catalysis, with turnover numbers on the order of 40 000 under both anaerobic and aerobic conditions.

FeFe]-Hydrogenase Mimetic Metallopolymers with Enhanced Catalytic Activity for Hydrogen Production in Water.

Electrocatalytic [FeFe]-hydrogenase mimics for the hydrogen evolution reaction (HER) generally suffer from low activity, high overpotential, aggregation, oxygen sensitivity, and low solubility in water. By using atom-transfer radical polymerization (ATRP), a new class of [FeFe]-metallopolymers with precise molar mass, defined composition, and low polydispersity, has been prepared. The synthetic methodology introduced here allows facile variation of polymer composition to optimize the [FeFe] solubility, activity, and long-term chemical and aerobic stability. Water soluble functional metallopolymers facilitate electrocatalytic hydrogen production in neutral water with loadings as low as 2 ppm and operate at rates an order of magnitude faster than hydrogenases (2.5×105 s-1 ), and with low overpotential requirement. Furthermore, unlike the hydrogenases, these systems are insensitive to oxygen during catalysis, with turnover numbers on the order of 40 000 under both anaerobic and aerobic conditions.

Hydrogen Evolution Reactions Catalyzed by a Bis(thiosemicarbazone) Cobalt Complex: An Experimental and Theoretical Study

The synthesis and characterization of a dinuclear bis(thiosemicarbazone) cobalt complex [Co2 L2 (NCS)2 ] is reported. This complex exhibits significant catalytic activity for hydrogen production in DMF by using triethylammonium (Et3 NHBF4 ) as the proton source. Cyclic voltammetry data allowed a maximum turnover frequency of 130 s-1 for 1 m proton concentration to be determined. The catalytic nature of the process and the production of dihydrogen were confirmed by gas analysis during controlled potential electrolysis experiments. Quantum chemical calculations show that the complex displays a ligand-assisted metal-centered reactivity and supports a catalytic mechanism involving ligand-based reduction and protonation steps followed by metal-centered processes.

Microwave Treatment on Co–B–P Catalyst to Enhance Catalytic Activity for Hydrogen Production by Hydrolysis of Nabh4

In this study, a microwave treatment was chosen as an alternative method to synthesize Co-B-P catalyst for hydrogen production from hydrolysis of sodium borohydride (NaBH4 ) for the first time. The effect of gas, treatment time, and microwave power, amount of catalyst and temperature on the catalytic activity of Co-B-P catalyst was investigated under microwave treatment. The synthesized Co-B-P catalyst was characterized by XRD, SEM, EDX, BET and FTIR measurements. In the presence of Co-B-P catalyst, hydrolysis of NaBH4 under microwave treatment was completed in 9 minutes whereas it was completed in 16 minutes under normal condition. It was found that the value of activation energy is 16.211 kJ*mol-1.

Morphology-dependent catalytic activity of plasmonic MoO3−x for hydrolytic dehydrogenation of ammonia borane

Series of plasmonic MoO[Formula: see text] particles have been prepared by a facile solvothermal method to produce hydrogen via hydrolytic dehydrogenation of ammonia borane. Interestingly, the as-prepared MoO[Formula: see text] particles present various morphologies, i.e. flower, schistose and nanorod by simply tuning the reaction temperature and solvent volume ratio of distilled water and acetic acid. More importantly, these MoO[Formula: see text] particles with different morphologies exhibit various catalytic performances of NH3BH3 under the irradiation of visible light. Particularly, the flower-like MoO[Formula: see text] microstructure possesses the best catalytic activity for hydrogen production probably owing to the relatively large surface area and strong LSPR in the visible region.

Hydrogen Production From catalytic reforming of greenhouse gases (CO<sub>2</sub> and CH<sub>4</sub>) Over Neodymiun (III) oxide supported Cobalt catalyst

Hydrogen production from CO2 reforming of methane over 20wt%.Co/Nd2O3 has been investigated in a fixed bed stainless steel reactor. The 20wt%.Co/Nd2O3 catalyst was synthesized using wet impregnation method and characterized for thermal stability, textural property, crystallinity, morphology and nature of chemical bonds using techniques such as TGA, XRD, N2 adsorption-desorption, FESEM, EDX and FTIR. The CO2 reforming of methane was performed at feed ratio (CH4:CO2) between 0.1-1 and reaction temperature ranged 973-1023 K. The catalyst displayed good activity towards selectivity and yield of hydrogen as well as CO, a by product. The selectivity and yield of Hydrogen increases with feed ratio and reaction temperature. The 20wt%.Co/Nd2O3 catalyst displayed promising catalytic activity for hydrogen production with the highest yield and selectivity of 32.5% and 17.6% respectively.Keywords: Cobalt; Greenhouse gases; Hydrogen; Reforming;; Neodymium (III)Oxide

Electrospun carbon nanofibers containing Co-TiC nanoparticles-like superficial protrusions as a catalyst for H2 gas production from ammonia borane complex

Abstract Co - TiC nanoparticles (NPs)-like superficial protrusions were grown on the surface of electrospun carbon nanofibers to produce composite nanofibers (composite NFs). The composite NFs demonstrated good catalytic activity in hydrogen production through hydrolysis of an aqueous ammonia borane (AB) solution. Catalytic activities of composite NFs were compared with those of CoTiC/C NPs (composite NPs), Co/carbon nanofibers (Co/C NFs) and Co nanoparticles (Co NPs). The composite NFs showed the highest catalytic activity (0.4167 mol min −1 ) compared to CoTiC/C NPs (0.35 mol min −1 ), Co/C NFs (0.25 mol min −1 ), and Co NPs (0.13 mol min −1 ). The turn over frequency (TOF) value of the synthesized nanocomposite is determined to be 32.18 mol H2 min −1 (mol metal −1 ). Moreover, the composite NFs showed high stability, and could be reused for several cycles without makeup, reactivation, or regeneration. Kinetic studies showed that the rate of AB hydrolysis depends on the catalyst concentration and temperature; the activation energy was found to be ~ 26.19 kJ mol −1 .

Two-step steam pyrolysis of biomass for hydrogen production

In this study, different char based catalysts were evaluated in order to increase hydrogen production from the steam pyrolysis of olive pomace in two stage fixed bed reactor system. Biomass char, nickel loaded biomass char, coal char and nickel or iron loaded coal chars were used as catalyst. Acid washed biomass char was also tested to investigate the effect of inorganics in char on catalytic activity for hydrogen production. Catalysts were characterized by using Brunauer–Emmet–Teller (BET) method, X-ray diffraction (XRD) analyzer, X-ray fluorescence (XRF) and thermogravimetric analyzer (TGA). The results showed that the steam in absence of catalyst had no influence on hydrogen production. Increase in catalytic bed temperature (from 500 °C to 700 °C) enhanced hydrogen production in presence of Ni-impregnated and non-impregnated biomass char. Inherent inorganic content of char had great effect on hydrogen production. Ni based biomass char exhibited the highest catalytic activity in terms of hydrogen production. Besides, Ni and Fe based coal char had catalytic activity on H2 production. On the other hand, the results showed that biomass char was not thermally stable under steam pyrolysis conditions. Weight loss of catalyst during steam pyrolysis could be attributed to steam gasification of biomass char itself. In contrast, properties of coal char based catalysts after steam pyrolysis process remained nearly unchanged, leading to better thermal stability than biomass char.